Is it a security risk to post a gmail email address on the web? For example;
Well, 'security' means different things to different people. But be assured that if you place a naked email address like that on the web, it will be picked up by lots of spam bots and will attract endless spam. So normally you'd 'obfuscate' the address in some way—for example, by using JS to scramble it behind the scenes—although these methods only have moderate success, because your email address can be harvested 'manually' (meaning that a human, rather than a bot, can add it to spam lists).
A safer option is to provide a contact form that is processed with a server-side language like PHP. Then no one gets to see your email address except those you choose to show it to when you email them.
Security risk - No.
Spam risk - Yes. But to avoid spam, you can show an image with your email address.